import { diffLines } from "diff";
import { strict as assert } from "node:assert";

function color(text: string, c: "red" | "green") {
  const codes = { red: '\x1b[31m', green: '\x1b[32m' };
  return `${codes[c]}${text}\x1b[0m`;
}

/**Asserts two strings are equal and diffs them in the assertion error if they are
 * not*/
export function assertStringEq(actual: string, expected: string, msg: string) {
  if (actual === expected) {
    return;
  }
  const diff = diffLines(actual, expected);
  const assertionMsg = `${msg}\n` + diff
    .map(part => {
      if (!part.added && !part.removed) {
        return part.value;
      }
      const prefix = part.added ? "+" : "-";
      return color(`${prefix}${part.value}`, part.added ? "green" : "red");
    })
    .join("");
  assert(actual === expected, assertionMsg);
}

/**Catches any p Promise throws and instead returns those in a tuple*/
export async function ptry<TRet, TError = Error>(
  p: Promise<TRet>
): Promise<[TError, undefined] | [undefined, TRet]> {
  try {
    const result = await p;
    return [undefined, result];
  } catch (err) {
    return [err as TError, undefined];
  }
}